370 HOW CROPS GROW. 
8 5. 
# DIRECTION OF VEGETABLE GROWTH. 
One of the most obvious peculiarities of vegetation is 
that the roots and stems of plants manifest more or less 
regular and often opposite directions of growth. Roots, 
in general, grow downwards; stems, in general, upwards, 
though this is by no means a universal rule, both roots 
and stems oftentimes manifesting either tendency in dif- 
ferent points or at different times of their growth. 
Sachs describes the following mode of observing the 
directive tendency of root and stem. 
F, fig. 71, is a glass flask containing some water; it is 
closed above by a cork from 
which a young seedling is (— . 
suspended by means of a i 
wire. The flask stands upon 
a plate of sand, and it is 
shielded from the light by a 
paste-board cover, &, the 
lower edge of which is forced 
down into the sand. The 
water in the flask keeps the 
enclosed air in a moist 
state. In the experiment, a 
sprouted nasturtium seed 
(Tropeolum majus) having a 
a perfectly straight descend- ‘ 
ing radicle, was placed at “W NN TWIT 
night i in the apparatus with orca 
the radicle pointing upwards 
and the plumule downwards. The next morning the- 
seedling had the appearance of the figure. During the 
night the tip of the root curved over and the plumule 
sensibly raised itself By continuing a similar experiment 
Fig. 7 V1. 
